I know the producers of Pokemon wanted to keep the fifth Generation completely new (minus Pikachu), though there are many examples of possible evolutions and family tree's throughout Unova.
Obviously Luvdisc should be evolving into Alomomola ~ there's too much of a resemblance for them not to be related.
Basculin could do with an evolution.
Maractus could do with a pre-evolution.
Emolga could be related to Pachirisu in some way. One could have been pure-female, the other pure-male. Each of them evolving into the same Pokemon (of both genders).
Stunfisk could use an evolution.
Druddigon could use a pre-evolution.
Bouffalant could easily be related to Tauros, in much the same way that I've placed Emolga and Pachirisu together.
Obviously Luvdisc should be evolving into Alomomola ~ there's too much of a resemblance for them not to be related.
Basculin could do with an evolution.
Maractus could do with a pre-evolution.
Emolga could be related to Pachirisu in some way. One could have been pure-female, the other pure-male. Each of them evolving into the same Pokemon (of both genders).
Stunfisk could use an evolution.
Druddigon could use a pre-evolution.
Bouffalant could easily be related to Tauros, in much the same way that I've placed Emolga and Pachirisu together.